The present invention relates to a computer system for providing a plurality of storage areas, and more particularly to a technique that updates the storage areas together.
In order to prevent the loss of data, as one of methods for forming a backup of a volume that stores the data, a method of forming a snapshot is exemplified. The snapshot means an image of the volume at the time of forming the backup. Since the snapshot is used to recover the damage of a file system, the snapshot is ordinarily used only for reading the data.
Further, the snapshot can be greatly utilized when the data is copied without a view to obtain the backup. For instance, a case is supposed to construct a plurality of test environments. However, since the snapshot is used only for reading as described above, if test data can be updated, it is convenient to employ the test data.
JP-T-2005-529410 discloses a technique that a differential volume for storing updated data is provided as well as an original snapshot only for reading to provide a snapshot that can be updated. In the technique disclosed in the patent literature 1, when a plurality of snapshots are provided, an area of a differential volume is reserved for each of the provided snapshots to store the updated data so that the snapshots can be individually met.
As a specific example, when software is developed by three development teams, a case that the technique disclosed in the JP-T-2005-529410 is applied thereto will be described. Further, each development team carries out a development by using an originally existing program serving as a base. At this time, three duplications (snapshots) of the program (original data) as the base are formed respectively for the development teams and the one original data is respectively pointed thereby. Then, when a certain development team adds a change to the original data, changed data is stored in the differential volume by considering the changed data to be a difference so that the snapshot can be updated.